Method of drawing glass.



R. L. & F. J. PRINK.

METHOD OF DRAWING GLASS.

APPLICATION FILED MAR.18,'1910.

'9'?2,616, a Patented Oct. 11,1910.

2 SHEET8SHEBT 1.

wfizesses fimm 9L I Ming;

R. L. & F. J. FRINK.

METHOD OF DRAWING GLASS. APPLICATION FILED MAR. 18, 1910.

Patented Oct. 11, 1910.

2 SHEETS-SHEET 2.

\Tllllllll" eflicientsof expansion of thematerial of which such bait is constructed, usually iron,-

\ rrn STATES PATENT FFICE! ROBERT L. rnmx AND manna. FRINK, or LANCASTER, 01110.

METHOD or DRAWING GLASS.

Specification of Letters Patent-. Patented Oct, 11, 1910.v

Application filed March .18, 1910. Serial no. 550,133. a

To all whom it may. concern:

Be it known that We, ROBERT L. FRINK vented a new and useful Improvement in Methods of Drawing Glass, ofwhich'the following isa specification, the principle of the invention-being herein explained and the best mode in which we have contemplated applying that principle, so as to distinguish it from other inventions, Y

A's'is well known, one of the more serious difiioulties encountered in drawing glass cylinders; by machine, in place of. blowing "them by hand as in the old method of manufacturing window glass, is the prevention of the breaking'otf-of the glass from the bait 1 or pipe by'means of'which it isv being drawn.

This difliculty arises fromthe difierent coand' the glass of the cylinder. So long as such glass remailisfabove the temperature where it comesto' a set,-;tl1e' novel, asthe thickened portion ofthe cylinder in contact with the bait is called,- can' accom modate' itself to chan'gesin the relative diameter of itself and the bait; Once, however, such; glass has setfthe further progress of the cooling 1 operation inevitablyinvOlved the production of such -strains inthe glass cornposing the novel, as will cause a fracture in thecylinder. Aside from the directly'disa'strous consequences of such fracture which is apt to 'run .in Variousdirections, lengthwise aszwell as transversely, of the cylinder, or roller, the resultis-usually the breaking away of thecylinder from the bait, and the ume also. This uniformity in heatlng efl'ect" complete loss. of the product.

It has heretofore been proposed to. control the cooling of the bait both by the conservation of the heat" received either previously or incidentally to the dipping of the bait inthemolten glass at the beginning of the draw and by the application ofheat frdm .an outside source to such bait. during the draw. The former method involves the use of .-an inclosure' of heat insulating materialfor the bait and contiguous portion of the cylinder; while asone example of the latter f method, reference may-be made to the pro- Another arrangement for thus-applying heat to the bait consists of an electrical heating device contained within a hollow bait, as shown in the patent" of R. L. Brink No. 915,282 and the use of an electric current as the heating medium has also been at-' tempted by passing a current through af resistance coil. encircling the bait adjacent to the latters line of contact with the cylinder, much as the'gasburners'are disposed in the arrangement previously described. None of these arrangements,- whereby the heat is: applied to the bait gives satisfactory results in practice, although by the arrangementof the heati'ng coil charaoterizing'the structure ofthe patent referred to above,-an

approximation to theideal condition desired has been reached. It willbeunderstood, of

course, that the control 'of the temperature of the bait is a very delicate matter 'in View of the fragile character of the glass, the. various strains introduced by. the cooling of the'wa'lls of the cylinder, and the not-inconsiderable strain" roduced b the increased weight of the 'oy nder'or ro er and the increased viscosity of the bath, as the draw pro- 'gresses. lVe have found, accordingly, that it is essentiahif successful results are to be obtained" in maintaining adhesive and. cohesive contact between: the cylinder and the bait during more than the relatively short;

period required for the temperature naturally to fall below the'point of set in the gl-ass',- that the. entire bait body be maintained ata uniform temperature, 'sothatjthe duced by {variation in temperature may be we have found can be secured by constituting of the bait itself the resistance'member ing electric'current is being passed. a proper construction, then, of such bait mem- J contraction and expansion of the bait pro- I in an electric circuit through which .a heat her and disposition of the leads fromfthe circuit counected'therewith. a substantially uniform flow'of the current through the en}- tire length of the bait may be secured and 1 thus the results referred to above rendered possible. p

' Various arrangements ofapparatils may be utilized in connection with our'li rnproved method, two slightly difl'erent' formsbein shown in a co-pending 'applica-tion,"S eri-a' 11 0,

used. v

In said annexed drawings-:Figure 1' is a front elevation of glass drawing mechanism including an improved construction of bait adapted for the carrying on of the the subject matter of the second of the copending applications above described; Fig. 2 is a side elevation of such mechanism; Fig. 3' is a vertical sectional View of the bait member proper, with'a portion of the cylin der attached ft'hereto; Fig; 4 is a transverse section of theVsame taken on the line 4."4,

Fig. and {Fig 5 is a vertical sectional view of a detail.

The mechanism shown in Figs. 1 and 2 consists in general of a vertically recipro cable cage A from which the bait B is suspended so as to be movable toward and from the drawing pot C in which is contained the bath of molten glass from which the cylinder is to be drawn. The 'term drawing pot here employed in a. generalsense to mean any suitable receptacle whether connected by a conduit directly with the glass tank, or arranged to be supplied by means of a ladle, or otherwise. Two vertical ways or guides at are provided for the case, which is formed to engage therewith at its respective ends, while a cable a operated by a suitable hoisting mechanismat a 'fzproper rate of speed is similarly provided for raising and lowering the cage. In ad- 1 dition to the foregoing, two electric conductors in the form of trolley wires D, are provided to the rear of the path of travel of the cage and parallel with said ways.

In the approved construction illustrated, the cage comprises simply a frame made up 'of'two transverse bars a suitably joined toether and braced by vertical bars a Two intermediately positioned vertical bars a are provided jwith forwardly projecting brackets of in which are .formed open trunnion bearings adapted to receive suitably formed lugs b on rod-like arms 5 that eX- tend upwardly from the bait body. As a result of this'construction, such body, it will be seen, is capable of oscillation in the plane of Fig, 2. Such. oscillation, however, is limited in a rearward direction by a stop present process, such specific bait forming -ber Z2 illustrated 1n figures ust named consists arm extending downwardly Tofacilitate the removaland attachment of the bait, or other manipulation thereof, it is provided with two handles 6 as shown in Figs. 1 and 3. The two brackets a that,

thus serve to support the bait body are insulated from each other and from'the frame of the cage, and are connected with the secondaries, or, in effect, themselves form continuations of the secondaries, of two transformer coils D, carried directly by the cage. The primaries d of such transformer lead to two trolley arms d adapted to movably contact with the correspondingly disposed trolley wires, Variations in the coils themselves, whereby. their transforming effect may be adjusted, is provided. for by means of switches d carried directlyon the cage, while a rheostat d is introduced into the circuit D that includes the two trolley wires, sothat the current supplied to theapparatus from the generator D or other source of current, may also be varied incharacter. Such trolley wires are preferably shorter than the range of movement of the cage. To this end simply a breaker (Z6 is introduced into each trolley wire, in order that the movement of the trolley. arms may be in no wise interfered with, although various other means for interrupting the connection through the transformer on the cage will readily suggest themselves as a substitute forthis.

The preferred construction of baitillustrated in connection with the foregoing drawing mechanism will be seen to comprise a body portion of general cylindrical form,

preferably constructed of sheet metal or equivalent homogeneous electro-conductive material. Such body carries the handles 6 one on its top and the other on the side, to which reference has been previously made. Such top, or cover, may'also be provided, if desired, with means, as an adjustable slide bar 6 whereby an opening of variable area is formed therein. To the lower edge of the body portion is firmlyriveted a flange b of angular cross section,- such flange preferably projecting outwardly from the body, and to said flange in turn is secured the bait memproper. The latter in the form simply of an attenuatedmetal band or ribbon in the form of a continuous circle, to the upper edge of which are riveted, or bett'er vstill welded, a series of boltsqbf; "The threaded ends of the latter are secured to,

I but i electrically insulated from the flange,

just descri be'd as being riveted-to-theilower edge v of the bait body,- (by a be ng: passed through bushings N5 of; insulating material, a

while the nuts b rest on similar washers b", as is shown in Fig. 5. As is further clearly illustrated in said figure, such bushing fits loosely in the hole provided therefor in the flange, and the bolt may also fit loosely in the bushing, so that a certain amount of transverse movement is permitted the bait member either as a whole, or as to a portion,

thereof, quite independently of the remainder. All this, however, is without in the least affecting the-solidity with which said bait member is supported in a-vertical clirection. The two arms 5 that extend upwardly from such body 'and pivotally support the same from the cage, are connected attheir lower ends to diametrically opposite portions of this band, so as to have good electrical contact therewith but said arms are otherwise, like the band, entirely electrically insulated from the body, the clamps Z) whereby they are securedto the latter hav-' ing bushings of insulating material. It will thus be seen that when the bait is in place suspended from the cage, and the trolley arms are in contact with the respective trolley wires, the electric circuit, including the dynamo or other generator is closed throughtransforming coils D, the brackets (P arms 'bj and the bait member connected with the lower'ends of the latter. The currentwobviously"divides and flows in multiple 7 through such-bait, but care is taken to have the respective portions thereof substantially equal in length and in cross section so that the heating eifect of the'current thus passed therethrough is substantially uniform throughout thewhole circumferential extent of the band.

As a result of the manner in which the bait memberproper, consisting in the form under consideration of a thin metal band or ribbon, is attached to the body portion of the bait, it will be obvious that such band is not only electrically insulated from said body portion, but substantially heat-lnsulated also, by reason of the relatively small heat conducting capacity of the spaced bolts or lugs b that constitute the sole physical connection between such member and body portion. 1

Having thus described the general structural features of our improved glass drawing mechanism with particular regard to details of the bait which constitutes the important feature of such mechanism, the method of operation of the apparatus may be next noted. The bait having been hung in the cage, is preliminarily adjusted so that of the bait member to which such arms are plane, and if necessary additional weight maybe attached on one side or the other tov secure this result.

The cageis permitted to descend until the. if I lower edge of the bait dips into the bath of glass in the drawing pot or receptacle C, ad

hesive and cohesive contact of the glass, that thereupon forms the novel of the cylinder,

being secured with boththe inner and outer faces of the bait member. After reversing the movement of the cage and bait, or in other words, after the draw proper is begun, the current is turned on so as to pass through the bait member, such turning on being timed to precede any excessive drop in temperature, the temperature at which it is desirable to maintain the bait during the draw being above the second point of tension in the glass, that is above the point where the glass comes to a set; glass men generally speaking of glass as having two points of tension, the first point being from 1200 to 1400 degrees, Fahrenheit, where de-vitrification, or crystallization, takes place, andthe second being in the neighborhood of 900 degrees, Fahrenheit. The volume and character of the current that is passed'through the bait is accordingly regulated, having due regard to the electrical resistance of the latter, so as to'maintain said bait at a temperature above such last-named point, and thus enable the glass in the novel, whether contacting with the inner or outer face of the bait, to accommodate itself without rupture to any relative displacement of said member incident to a change in their common temperature. This regulation of the electric circuit, and thus of the temperature, is effected, in the first .place, by adjusting the transformer coil connections by means of switches (i so as to provide with the current available in the main line, a current in the secondaries, which include in circuit therewith the bait member proper, a current ap-' propriate to the size of the bait, 'or in other words, the size of. the sheet or cylinder being drawn. For varying the current during any particular drawing operation, with the transformer coils thus adjusted, the 1'heo stat d is utilized. v

The rate of the draw, as the bait emerges from the bath of molten glass is controlled so as not only to permit. the formation of an adequate novel, but also to cause a slight thickening of the cylinder walls at ppints equally spaced from and located just belowsuch novel, as clearly shown in Fig. 3. Thereafter the speed at which the bait is raised is made such as'to produce glass of the desired thickness. 1 In place of thus .nua-king the walls thicker than normal a -point below the novel they may be drawn thinnenm The diagrammatic sectional views of the bait member with novel attached, shown in Figs. 3 and 4, are designed to render'clear the effect of changing temperatures in this portion of the cylinder, or sheet, of glass being drawn,'as the case maybe, and thus the significance. of our improved method of controlling such temperatures rendered'posslble by the apparatus hereinbefore described. The section, of thebait member therein'appearing, is shown as inclosed toapproximately' the degree actually toundin practice by the glass formin the upper end or novel'of the cylinder. af'course, both this member and-the novel will initially,

that is when the member is dipped into the bath of molten glass, have approximately the same temperature as that of such bath.

Immediately, however, the drawing process proper is begun, the member and the novel begin to lose heat by radiation and 'convec' vtion, and in a limited degree, by conduction through the bolts, rivets, or equivalent means whereby the member is attached tojtheflbody portion of the bait. It has been explained, however, that this latter form of loss is 'reduced to a minimum by the constructioniof such attaching means.

gresses, a. corresponding-change occurs in the cubical contents or three-way dimensions of both the baitmember and the novel, but owing to the different materials of which these are respectively composed, the band constituting the member will tend to contract more than the glass. The -1nner portionjof the novel, 15, hence, put under a compression strain and the outer portion under a tension strain, which strains if allowed to become too great produce a rupture at the point'of attachment of the novel to the bait.

This tendency to rupture, it has been explained, is avoided t y maintaining the temperature of the bait and the attached glass above the point at which such strains are present to a harmful degree, and'in this way the glass is maintained in contact with the bait member. This contact may be adhesive or cohesive, with or without any OXld intermediate the glass' and bait member, hence 'by the use of the words adhering or immediate in the claims, we 'intend to include and cover any direct attachmentbetween the bait and glass without the employment of clamps or other mechanical attaching connecting device. This very tendency to rupture, however, upon allowing the tempera-' ture of bait and novel to fall-blowQsuchpredetermined point, we utilize. to sever the cylinder from the bait upon the .coiiclu'sion of the drawing operation. In other-words, it is a matter of but a relatively few moments after the current'is turned 'ofi'thr'oug'h' the bait, before the cylinder will snap oiffrom the bait, and byproperlj controllin'g the resulting fracture, as'by making the As such cooling pro- -walls thicker below the novel, the rather difiic'ult-task of severing the cylinder from the bait, involved in the prevailing practice, is easily accomplished.

A part of the advantageous results that have been obtained in' practice by our im' provedconstruction of bait, is attributable to the flexibility of the bait member proper and to the-mode of attaching said member to the support, or body member, whereby the former is permitted'to accommodate itself by flexurein ahorizontal plane to varying conditions of'strain in the cylinder or "roller" suspended therefrom. WVhile a satisfactory 1 degree of flexibility may be obtained where the independent shifting movementbf such bolts in thesupporting flange, as has been hereinbefore described. "By reason of this mechanical adjustability of the bait, We are warranted in referring to our 'im rov'ed -method as one wherein the head oft e cyl- /inder is flexibl supportgas-wel as one'in which the' tern-[- 'perature ofgthe bait member, that forms the attached to the thawingmeans I of such attachment, .isartificiallyregulated bypassing a. heating electric cur rent therethroughyj f Other modes. of applying. the principle of our invention ma. fbe. 'employed insteadof' the one explains tjc'hange bein made as. regards the process herein disc losedpp'rovided the-istepiof'steps,stated by: any one of 2. The method of draw ng glass, which theyieldingcharacter of the attaching bolts I alone is relied on, we' prefer to provide for consistsin lowering into and raisingv from a bath of molten glass a bait member having a co-eflicient of expansion ditierent from that of glass, and artificially maintaining the temperature of said member within the glass at. a point such'that the" glass in contact therewith is kept from setting and thus enabled to accommodate itself-without rupture to any relative displacement of said member incident .to a change in their temperature,

substantially as described.

SgThe method of making glass cylinders, which consists in lowering. 1nt'o and' rais ng- [from a bat'hoi moltenglass a" circular .me-

tallic bait inemberhaving a co-eflicient of expansion different fronrthat of glass, and passing a heating electric current through said member, said current being regulatedto I maintain the temperatureof said 'memb'ergflt' such a point that the glass in contact there with iskept from setting and thus enabled to accommodate itself Without rupture to any relative displacement of said member incident to a change in their temperature,

and then interrupting'such current whereby ceeding with the draw; and artificially heating said member during all of such draw save the initial stage of forming of the novel, substantially as described.

5. The method of making glass cylinders, whi-chpconsists in lowering into a bath of I molten glass a bait member having a coeflicient of expansion diiferent from that of lass; raising said bait member from such bath .with the novel clinging thereto and proceeding with the draw; and passing a heating electric current through said mem berwhen the glass in such novel has cooledto approximately the second pointof ten-- sion', said current being regulatedto maintain the temperature of said member at a priint such that said novel is kept from setting and-thus enabled to accommodate itself without rupture to any relative displacementof said'member incident to a change in the latters temperature and that of such novel, substantially as described.

6. A method of drawing glass consisting in lowering a bait member having a coefiicient ofexpansion-difierent from that of glass, into a bath of molten glass whereby the glass is caused to'adhere to the bait, l'illS-a ing the bait with the attached glass, and

' maintaining the bait at, a substantially equable'iemperatur'e' throughout the contacting area, such temperature being sufficient to prevent the ,glass fromxsetting whereby the said glass may accommodate ltselfwithout rupture to any relative displacement of' saidbaitmember incident toany fluctuation of temperature therein,

7. The methodof drawing'glass articles consisting in lowering a bait into a bathof molten glass whereby the glass is caused to adhere thereto, raising the bait with the adhering glass, and heating the-bait by a heating electric'current passing through same,

' whereby the glass is maintained in a mobile condition and prevented from setting.

8, The method of making glass cylinders, which consists in lowering into and raising from a bath of molten glass a baitmember havinga co-eflicient of expansion different from that of the glass; electrically main taining the temperature of said member during the draw at a point such 'that' the glass in" contact therewith is-kept from setting and thus enabled'to accommodate itself without rupture to any relative displacement ofsald member incident to a change in their temperature; vand then permitting the temperature, of said member to drop when'the draw 'is concluded, whereby-the" cylinder is causel to break off from said memberythe cylinder walls being drawn of tion thus in' contact with said member. '1"

'an increased tlnckness at -points equally "spaced from and located just below the poi-,'

9. The method of making glass cylinders which consists in lowering into and raising from abath of molten glass :1 bait men'iber of homogeneous electro-conductivity mate jf rial having a co-efiicient of expansion tdif vferent from that of the glass; passing a heating. electric current through said me1 her, said current being regulated to mamtain the temperature of said member during the draw at a point such that the glass in "contact therewith is kept from settin and thus enabled to accommodate itself without rupture to any relatii'e displacement of said member incident to, a change in their tem- 4 .perature; and then interrupting the passage of such current through said member when the draw is concluded, whereby the temperature'of the latter is permitted to drop and the cylinder is caused to break ofl'i from said member; the cylinder wali',

drawn of an increased thickness at points.

equallyspaced from and located just below the portion thus in contact with saidmerh ber. 10. The method of makilf lg glass cylin ders, which consists in lowering Into and raising from a bath of molten glass a bait member of metal having, a co-efiicient of expansion different from that of the glass the novel of the cylinder being drawn having adhesive and cohesive contact with-both the inner and outer faces of said n1e11 1be'r;.artificially maintaining'the temperature of said member during'the draw at a point such that the glass in such cylinder novel is kept from settingmnd thus enabled to accommodate itselfwvithout rupture to anyrelative displacement of said member incident to a change in the temperature; and then interrupt-ing the passage of such current through said memberwhen the draw is concluded.

llt

11. The method of making glass cylin ders, which consists in lowering into and raising from a bath of molten glass a bait member of meta'l having a' co-etiicient of expansion dififerent from that of the glass, the novel of the" cylinder being. drawn having adhesive and cohesive contact with both the inner andfouter faces of said member arti.

- ficially maintaining the temperature of-said member'during the draw at a .point' such that the glass iusuch' cylinder novel is kept from setting and thus enabled to accommoc. date itself-withoutjmpture ,to' any relative (displacement ofsa-idqmember incident to a change ini-their temperature and then interrupting Qthg passage of such current through saidiniember when the draw is con-- cluded, the portion of such cylinder'novel in cont-acflwith the inner face of saidmembenis put under compression ow- 2,0 'at points equally spaced from and located Jingto the relative'greater contractibility of said member, whereby the cylinder is caused v to break off from said member, the cylinder walls being drawn of an increased thickness v just below' such novel.

12.,A= method of drawing glass cylinders consisting in lowering into a bath of molten glass a bait member initially heating. such member by contact with the molten glass, raising the bait ,with the head of the cylinder attached theretoand allowing the novel I to form and'then electrically maintainingthe temperature of suchqmember thatv the portion inclosed by the novel shall be of such temperature as to' prevent. rupture,

throughoutthe remainder of the draw.

and glass, and mobile attachment of the article to the support, by an electrical heating current passing through the bait.

Signed by us this 15th day of March, 1910. ROBERT L. FRINK.

FRED J. FRINK,

Attestedby:

V. K. MARTIN, CHARLES "axnmss. 

